Liftgates and other doors on vans and other utility vehicles are large and heavy. Their weight is increased by windows, window wipers, defoggers and other equipment. Their hinges with a horizontal pivot axis at the top of the liftgate cause a fully open liftgate to be above the reach of many people. Power liftgate opening and closing systems are needed to reduce the effort required to manually open and close heavy liftgates. Power closing systems are also needed by all but the tallest people to close liftgates that are above their reach.
A number of power systems have been proposed for opening and closing vehicle liftgates. These systems include complicated linkages in combination with a manual window crank mechanism. Such linkage systems are slow, require substantial effort to use and are unreliable.
Automotive deck lid closures with gear trains, gear racks and drive pinions have been proposed. Such systems are heavy, expensive and require a substantial amount of space.
Cable drives have been proposed for use on vehicle liftgates as well as on truck or deck lids. These units generally have not maintained tension on the cables. When cables become slack they can get kinks, catch on cargo in the vehicle, become misrouted and have limited control over the position of open liftgates and deck lids. Manual opening and closing is difficult at best and operation during a vehicle electrical failure may be impossible.